Magnetic resonance (MR) imaging employing T2* weighting is used to provide enhanced contrast in techniques such as blood oxygenation level dependent (BOLD) contrast imaging, iron overload imaging, detection or imaging of superparamagnetic iron oxides (SPIO's) in molecular MR imaging, and so forth. In BOLD imaging, contrast originates from the paramagnetic nature of deoxyhaemoglobin in red blood cells, which perturbs the main magnetic field, leading to a local reduction in main field homogeneity and increased T2* decay (that is, short T2*). Oxygen, on the other hand, effectively shields the paramagnetic haemoglobin, yielding an increased T2*. Thus, a contrast between oxygenated and deoxygenated blood can be obtained by T2* weighted imaging, which elucidates local tissue oxygen consumption.
Various species in a typical biological subject exhibit a range of T2* times. Species with long T2* times are of interest for BOLD and some other T2* weighted imaging techniques. Existing T2* weighted images typically rely upon the enhancement of long T2* contrast by use of long echo time (TE). For example, spoiled gradient echo sequences (SPGR) with long echo times or echo-planar imaging (EPI) methods are used for T2* weighted imaging.
However, these sequences may not provide optimal signal-to-noise ratio (SNR), and are susceptible to flow artifacts due to the long TE. For BOLD imaging of the brain, this may be acceptable due to typically low flow rates in brain tissue. However, for BOLD imaging of regions of faster blood flow, such as cardiac BOLD imaging, flow artifacts can be so pronounced as to prevent successful BOLD imaging.
Accordingly, it would be useful to provide T2* weighting reflective of long T2* species without relying upon long echo times, as is done in existing T2* weighting approaches.
The following provides new and improved apparatuses and methods which overcome the above-referenced problems and others.